Ever more stringent regulations regarding permissible pollutant emissions by motor vehicles fitted with internal combustion engines make it necessary to keep the pollutant emissions as low as possible during operation of the internal combustion engine. One of the ways in which this can be done is by reducing the emissions which occur during the combustion of the air/fuel mixture in the relevant cylinder of the internal combustion engine. Another is to use exhaust gas post processing systems in internal combustion engines which convert the emissions which are generated during the combustion process of the air/fuel mixture in the relevant cylinder into harmless substances. Catalyzers are used for this purpose which convert carbon monoxide, hydrocarbons and nitrous oxide into harmless substances. A prerequisite for catalytic converters to be able to do their job well is that on the one hand a predetermined operating temperature of the respective exhaust gas catalyzer is reached and on the other hand however no overheating occurs either. For this reason it is important to determine as precisely as possible the temperature of the exhaust gas in the exhaust gas tract in which the exhaust gas catalyzer is arranged.
In addition, with modern internal combustion engines, diagnosis during the operation of the internal combustion engine is required. In this context monitoring is undertaken as to whether misfires are occurring. The causes of such misfires can differ, such as for example a fault in the injection system of the internal combustion engine, for example brought about by an undesired non-opening of the injection valve. This can then lead to an incorrect metering of fuel and thus prevent ignition of the mixture present in the cylinder. The fault can however also be caused by a fault in an ignition system of the internal combustion engine. If such misfires are detected within the framework of diagnosis this can lead to a fault being entered and to a request to the driver of the motor vehicle in which the internal combustion engine is arranged to find a workshop or also simply cause an incorrect entry which is read out within the framework of the next customer service.
A method is known from DE 199 13 746 C2 for recognizing misfires which degrade exhaust quality or damage catalyzers in internal combustion engines. A lambda probe voltage of a lambda probe arranged downstream from an exhaust gas catalyzer is determined in relation to a misfire detected. The misfire can for example be detected by investigating the uneven running. Depending on the Lambda probe voltage a misfire is then deduced as a result of a combustion error, an injection error or another type of error.